In general, a drug disperses throughout the body after administration, and it would be desirable for an anti-cancer agent and other drugs with strong side-effects to remain in high concentrations at the site of action without dispersing to other sites. A variety of efforts have been made to concentrate the drug locally. One method which has been attempted is to use a magnetic particle to concentrate the drug locally by means of a magnetic force exerted from outside the body. For example, it is possible to include a magnetic material together with the drug in liposome which is then administered and guided to a locality by the magnetic force, thus increasing the local concentration of the drug (see for example Journal of the Japanese Oral Surgery Society, February, 1997, pp. 55-61).
On the other hand, a technique is also known for modifying with an antibody the surface of a magnetic bead consisting of a polymer and a ferrimagnetic material such as magnetite and the like, and using an antigen-antibody reaction to isolate and produce a cell, and this technique has been applied to HLA typing, selection of hematopoietic stem cell and the like (see for example Biomaterial, February, 2003, pp. 113-119).